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ENGINEERING, CS 2023 HSC 22a

Previously, children's playground structures were constructed from 'treated pine' logs. The logs were treated with a copper chromium arsenate (CCA) solution which resisted fungi, insect attack and decay.

  1. Outline why new materials are being used to replace CCA treated logs in children's playground structures.   (2 marks)

  2. Justify a suitable material to use for a playground structure which will be exposed to the weather at all times.   (3 marks)

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i.     CCA materials contain arsenic.

  • Arsenic is a carcinogen/poison and not considered suitable for use in children’s playground structures.
  • Other modern plastic materials also have superior characteristics for playground use including better resistance to insect attack and improved traction. 

ii.   Compact Laminate is suitable material.

  • It is made of softwood and phenolic binder provides excellent stability over time and good abrasion resistance.

Other possible answers include:

  • Finished hardwood: resistant to corrosion and degradation in bright sunlight while also being very tough and wear resistant.
  • UV stabilised High Density Polyethylene: Provides bright colours, formability of complex shapes and low maintenance.
  • Stainless Steel: Provides good corrosion resistance, strength and wear resistance.
  • UV Stabilised ABS: Strong and light with excellent water resistance.

Show Worked Solution

i.   CCA materials contain arsenic.

  • Arsenic is a carcinogen/poison and not considered suitable for use in children’s playground structures.
  • Other modern plastic materials also have superior characteristics for playground use including better resistance to insect attack and improved traction.  

ii.   Compact Laminate is suitable material.

  • It is made of softwood and phenolic binder provides excellent stability over time and good abrasion resistance.

Other possible answers include:

  • Finished hardwood: resistant to corrosion and degradation in bright sunlight while also being very tough and wear resistant.
  • UV stabilised High Density Polyethylene: Provides bright colours, formability of complex shapes and low maintenance.
  • Stainless Steel: Provides good corrosion resistance, strength and wear resistance.
  • UV Stabilised ABS: Strong and light with excellent water resistance.

ENGINEERING, CS 2016 HSC 23b

This diagram shows the cross-section of a highway pavement drawn using AS 1100 drawing standards.
 

  1. Outline the properties of asphalt that make it suitable for highway pavement surfaces.   (3 marks)
  1. Why are geotextiles used in the construction of highway pavements?   (3 marks)
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i.    Successful answers should include 3 of the following:

Asphalt suitability

  • More durable than gravel and easier to lay than concrete.
  • Easily shaped and moulded to the contour of the road.
  • Can be driven on minutes after laying.
  • Can be easily repaired.
  • A smooth surface can be produced by pressing aggregate into substrate.
  • Flexibility allows for earth movement.

ii.   Reasons for using geotextiles:

  • Geotextiles are used to prevent the blockage of underground drainage by filtering silt from drainage below the surface.
  • They can also be used to prevent silt from undermining the road base, which can lead to road collapse.
Show Worked Solution

i.    Successful answers should include 3 of the following:

Asphalt suitability

  • More durable than gravel and easier to lay than concrete.
  • Easily shaped and moulded to the contour of the road.
  • Can be driven on minutes after laying.
  • Can be easily repaired.
  • A smooth surface can be produced by pressing aggregate into substrate.
  • Flexibility allows for earth movement.

ii.   Reasons for using geotextiles:

  • Geotextiles are used to prevent the blockage of underground drainage by filtering silt from drainage below the surface.
  • They can also be used to prevent silt from undermining the road base, which can lead to road collapse.

♦♦ Mean mark (ii) 38%.